This invention relates to the field of large video display systems of the type suitable for use in stadia. Such displays are usually formed by a large matrix of variable intensity display devices as, for example, incandescent light bulbs, fluorescent light sources, light-emitting diode sources, and the like. The display devices are driven by an electronic display system, usually computer controlled. The display system receives a video input such as the line feed from a network broadcast, a video tape recording, or a signal from a live action camera. The display system digitizes the video input, producing data corresponding to the intensity level of each picture element which forms a line in a conventional television raster. The number of picture elements or sampling points and the number of lines of the raster which are digitized and subsequently used by the display system are limited by the capacity of the system to handle the incoming video data in real time.
Because the video data rates are so high it has not heretofore been possible to utilize all of the available video information for displaying images on the scoreboard portion of the display system. Instead, large portions of the video information are simply discarded and, as a result, the display image was of rather low, although acceptable, resolution. For example, in early systems referred to below, approximately 75% of the available video data was discarded by the display system. That is, these systems utilized every other line of video data in one field. As is well known in the television industry, a complete frame of video information includes two fields which are interlaced to form the complete frame.
In such prior systems, even with the reduced quantity of data it was still necessary to provide a means for storing the selected data from each frame for a time sufficient to permit its transmission to the display device. In early systems, the digitized data for a frame was stored in a computer memory and subsequently transferred from the memory to the display devices. Typically, such systems employed minicomputers of the type manufactured by Digital Equipment Corporation, Maynard, Massachusetts, such as PDP 8 and 11. Although such computers are relatively powerful devices, their data transfer rates are too low to transmit as much digitized video information, on a real-time basis, as is required for high resolution video displays. As a result, the computer represents a limiting element in the system with respect to the rate at which digitized data can be transferred to the display elements.
One way of increasing the data-handling capacity of such systems is to substitute a high-speed random-access memory, often referred to as a full-frame buffer for the computer storage. This results in a speed increase which permits improved contrast, e.g., increased number of intensity levels and better resolution, e.g., more video data utilized. In such systems, the computer retains control of the system but is removed from the data path to the display board.
This latter approach wherein a buffer is utilized produces an acceptable display image but is still not totally satisfactory from the standpoint of being able to use sufficient video information to provide high resolution and high quality video displays.
It is desirable to provide a display system which is capable of utilizing substantial portions of the available video data for each frame. In order to do so, it is necessary that the system be able to digitize and transmit the digitized video information to the display board on essentially a real time basis. By real time basis it is meant that the need for a full frame buffer memory or a full frame computer storage element is eliminated and the digitized data is transmitted directly to the display board after appropriate selection of the portions thereof to be displayed.
It is accordingly an object of the present invention to provide a high resolution video display system which can receive video data, digitize it into the intensity level information, and transmit the digitized information to a display board on a real time basis.
It is a further object of the present invention to provide a system of the type mentioned in the preceding paragraph which does not require a full frame buffer memory interposed in the data path.
Another object of the invention is to provide a display system which can simulate enlargement of selected portions of a video frame by increasing the sampling rate for a line of incoming video data and utilizing additional lines which may, in other modes of operation, be discarded.
Still a further object of the invention is the provision of display system circuits which are programmable so that various user options can be set up merely by changing program data whereby resolution, enlargement, display sizes, intensity levels, and the like can be selected for particular applications.
A further object of the invention is the provision of a novel circuit, referred to herein as a rotator, which can cause a message to appear to travel across the video display in a manner which does not require the control computer to perform the data manipulation involved therewith.
Other objects and advantages of the invention will become apparent from the remaining portions of the specification.